The invention relates generally to shielding and more particularly to hybrid carbon nanotube shielding for cables.
CNTs are 1-dimensional, nanometer-scale, tubular-shaped graphene molecules that exhibit ballistic semiconducting and metallic electrical conductivity properties at room temperature. CNTs have extremely small size and extremely large specific surface area. CNTs are known to have extraordinary strength, including high strain to failure and relatively high modulus. CNTs may also be highly resistant to fatigue, radiation damage, and heat.
CNTs comprise sp2 covalently bonded carbon atoms in a hexagonal array and have a relatively low density of around 1,400 kg/m3. Due to void volume, spun CNT yarns, braided wire and manufactured sheet products can have densities as much as ⅔ lower than this figure. CNTs may be produced as single- or multi-wall tubular structures by a variety of synthesis methods and can have a length-to-diameter aspect ratio ranging from approximately 102 to 108. Having such a large range of aspect ratios, CNTs may be readily assembled into strands, threads and yarns, and braided into wires and woven into fabrics much like wool or other macro-scale fibrous materials.
The key to a successful lighter weight cable involves the use of an hybrid mechanical-electrical architecture employing a metallic foil for the shielding function, i.e., shielding effectiveness, and carbon nanotube (CNT) tapes for the mechanical function, i.e., holding the foil in place, as well as secondary shielding function. FIGS. 1 and 2 show schematics of the design configurations for a typical DC cable and for a coax cable, respectively.